I’m looking to add a gauge to an open position on my dash. When I remove the plastic cover and measure the hole it seems to be 60mm, or just over 2 1/3”. I see gauges with bezels of 2 1/4” but nothing larger until you get to over 3”. Has anyone installed into the smaller holes and what size gauge did you use?

The Pinz is metric. The hole in the dash is exactly 60 mm in diameter and in previous years this was the standard size for several gauges.
Some folks have installed Voltmeters to display the status of the onboard electricals, others have added a second fuel tank and use this hole for the corresponding gauge.
VDO nowadays offers most of these devices in 50 mm diameter, and you can purchase an adapter ring for 60 mm holes with them.

hope that helps

Cheers
Albert
========================My Pinz has NEVER been with any army